OTHER GLACIERS OF PRINCE WILLIAM SOUND 375
part extends at right angles to it with a length of about 13 miles and a width of from $ to 1$ miles. Facing the entrance is Chenega Island, north of which Dangerous Passage also connects Icy Bay with the northern portion of Knight Island Passage. The inner part of Icy Bay has a cove on the southern side which is separated from Port Bain-bridge by a narrow isthmus from one half to three fourths of a mile in width (Fig. 56). The head of Icy Bay, to the southwest of this cove is less than half a mile wide and ia terminated by a tidal ice tongue called Tiger Glacier. On the northern side of inner Icy Bay is a larger indentation nearly two miles in length and from one half to two miles wide, and partly cut off from Icy Bay by a high, rocky peninsula. Chenega, Princeton, and Tiger's Tail Glaciers terminate in this indentation, which is called Nassau Fiord. Small icebergs from this bay drift out into Knight Island Passage, sometimes being seen as far east as Latouche Island, along a channel regularly traversed by steamers. The depths of water in Icy Bay are unknown except at the mouth, in "Knight Island Passage, where the fiord is 1000 to 1350 feet deep,1 and in Icy Bay opposite the mouth of Nassau Fiord where it is 300 feet.8 The fiord walls are steep and the adjacent mountains rise to heights of several thousand feet above sea level.
Observations of Glaciers. The information about the glaciers of Icy Bay is based upon observations by Portlocks in 1787, Vancouver 4 in 1794, Seton Karr6 in 1886, Applegate6 in 1887, Glenn 7 in 1898, Grant and Higgins 8 in 1908, Perkins B in 1909, and the National Geographic Society's expedition10 in 1910.
Glaciers of Nassau Fiord—Chenega Glacier. Chenega Glacier is known to be at least 3 miles long, plus a continuation in unexplored snowfields, and is fed by two large tributaries, and at least one small one. It terminates in Nassau Fiord with a vertical ice cliff nearly half a mile in width and 135 feet high. It is a clean white ice tongue with no medial moraines and descends a steep slope of 500 or 600 feet in the last quarter of a mile, with severe crevassing. Above this the glacier has a more moderate slope. Many icebergs are discharged from this, the most active tidal glacier in Icy Bay. Around its terminus, and on a nunatak between its two chief tributaries, is an extensive barren zone; and the absence of vegetation throughout most of the lower slopes of Nassau Fiord indicate recent extensive retreat.
Historical evidence, reviewed later, indicates that Chenega Glacier, joining the ad-
i U. S. Coast and Geod. Survey, Chart No. 8550.
i Soundings by Capt. W. P. S. Porter of the steamship Yucatan -which took the Perkins party into Icy Bay in 1009. Personal communication from Mr. George W. Perkins, i Portlock, Nathaniel, Voyage Round the World, London, 1789, p. 240.
• Vancouver, George, Voyage of Discovery to the Pacific Ocean and Round the World, Vol. V, London, 1801, pp. 304-805; maps republished by Davidson (see below) Maps IV and V.
' Seton Karr, H. W., Shores and Alps of Alaska, London, 1887, pp. 228-229.
• Applegate, 8., quoted in Davidson's Glaciers of Alaska That are Shown on Russian Charts or Mentioned in Older Narratives, Trans, and Proc. Geog. Soc., Pacific, Vol. S, 1904, p. 23.
' Glenn, E. F., War Dept., Adj.-Gen. Office, No. XXV, 1899, map hi pocket.
' Grant, U. S. and Higgins, D. F., Glaciers of the West Coast of Prince William Sound, Bull. Amer. Geog. Soc., Vol. XT.TTT, 1911, pp. 410, 414-416; Tidewater Glaciers of Prince William Sound and Renal Peninsula, Bull., U. S. Geol. Survey (in preparation); also in H. F. Reid's Variations of Glaciers, Journ. Geol., Vol. XVII, 1909, pp. 670-671; also Maps in Bull. 284, U. S. Geol. Survey, 1906, Fig. 4 on p. 79; Ibid., Bull. 379,1909, PI. IV facing p. 88; Ibid., Bull. 443, 1910. PI. I facing p. 10 and PI. H, in pocket.
• Perkins, George W., Personal communication.
» Martin, Lawrence, Nat. Geog. Mag., Vol. TCKTf, 1911, pp. 551,555; Journ. Geol., Vol. XTX, 1911, p. 458.